. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. EECENT PROGRESS IN PHYSICS. 421 Unprepared carbon ' Carbon with nitrate of strontium Carbon Avith caustic potash Carbon with cliloride of zinc Carbon with borax in sulph. acid Distance of the carbon points. fa mm. 95 68 120 88 101 82 80 67 72 6i 932 139 353 274 160 75 624 159 1171 165 This table shows that on increasing the distance of the points the intensity of light and the force of current decrea
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. EECENT PROGRESS IN PHYSICS. 421 Unprepared carbon ' Carbon with nitrate of strontium Carbon Avith caustic potash Carbon with cliloride of zinc Carbon with borax in sulph. acid Distance of the carbon points. fa mm. 95 68 120 88 101 82 80 67 72 6i 932 139 353 274 160 75 624 159 1171 165 This table shows that on increasing the distance of the points the intensity of light and the force of current decrease. By most of the substances with which the carbon had been prepared, the arc of light was made more steady and allowed of a greater distance of the points, but the intensity was not greater, except with the carbon prepared with borax and sulphuric acid. But the results in the above table are only approximately accurate, since the changeable position of the most brilliant points at the origin of the arc may have prevented the light from acting with its full in- tensity upon the photometer. In another series of experiments, an abstract of which is given in the following table, this error was avoided, the arc of light having been directed towards the photometer by means of a magnet. In these experiments only 34 Bunsen's cups were used, the distance of the carbon points was not changed, and the intensity of the light was measured for different degrees of force of current. Intensity of liy:ht. Carbon with boracic acid. Carbon with sulpliate of 198 252 298 178 203 34 6 460 The carbon saturated with sulphate of soda was not heated to red- ness before use. It follows from these experiments that the intensity of light in- creases in a somewhat greater ratio than the force of the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly
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